The long-term objective of this application is to increase our understanding of how the host regulates immune responses to inflammatory stimuli, such as microbes and trauma, and to lay the foundation for advances in treatment of inflammation-related diseases. The current project focuses on the cellular and molecular mechanisms whereby progranulin (PGRN) and secretory leukocyte protease inhibitor (SLPI), two host-derived anti-inflammatory proteins, regulate the synthesis of IL-10 in macrophages in vitro and protect the host in systemic inflammatory disorders like septic shock. The hypothesis is that PGRN and SLPI are pivotal regulators of inflammation and tissue equilibrium through their ability to control IL-10 production. Four specific aims are proposed to test the hypothesis. The first aim will identify IL-10-regulating transcription factors (TFs) targeted by PGRN by (i) comparing LPS-induced association of known IL-10-activating TFs with IL-10 promoter between wild type and PGRN-null macrophages and (ii) a systematic search for novel TFs induced by the addition of recombinant PGRN using a series of 5[unreadable] and 3[unreadable] deletion constructs of the human IL-10 promoter-luciferase reporter. The second aim will investigate the role of PGRN in chromatin remodeling and histone modification of the il10 gene by comparing these modifications between wild type and PGRN-null macrophages. The third aim will investigate the role of PGRN and SLPI in the regulation of LPS-induced IL-10 induction by comparing LPS-induced IL-10 in macrophages expressing different amounts of SLPI or PGRN in vitro, or in wild type, SLPI-null or PGRN-null mice after LPS challenge. The fourth aim will examine the role of PGRN in systemic inflammatory responses and its IL-10 dependency. First, we will assess whether deletion of the pgrn gene affects survival of mice subjected to LPS-induced endotoxemia, and if administration of recombinant IL-10 or expression of an il10 transgene can ease the susceptibility of PGRN-knockout mice to LPS challenge. Second, we will determine if deletion of the pgrn gene affects survival of mice in cecal ligation and puncture-induced sepsis, and whether administration of recombinant PGRN can protect the mice from systemic inflammation-induced lethality. Such studies will provide important insights into the role of PGRN and SLPI in the systemic inflammatory response syndrome and aid in the development of novel strategies for effective interventions in sepsis and immunological paralysis that often follows.